Storage and assignment of control timing configurations in a multiple cell communications network

ABSTRACT

Example embodiments are directed towards a network node, and corresponding method, for a configuration of scheduling or control timing for a user equipment in a multiple cell communications network. The configuration of scheduling or control timing being based on at least two ordered sets of timing configuration numbers, each ordered set corresponding to a cell associated with the user equipment in the multiple cell communications network.

TECHNICAL FIELD

Example embodiments are directed towards a network node, andcorresponding method, for a configuration of scheduling or controltiming for a user equipment in a multiple cell communications network.

BACKGROUND

Long Term Evolution Systems

Long Term Evolution (LTE) uses Orthogonal Frequency DivisionMultiplexing (OFDM) in the downlink direction and a Discrete FourierTransform (DFT)-spread OFDM in the uplink direction. The basic LTEdownlink physical resource may thus be seen as a time-frequency grid asillustrated in FIG. 1, where each resource element corresponds to oneOFDM subcarrier during one OFDM symbol interval. In the time domain, LTEdownlink transmissions may be organized into radio frames of 10 ms, witheach radio frame consisting of ten equally-sized subframes of length Tsubframe=1 ms, as illustrated in FIG. 2.

Furthermore, the resource allocation in LTE is typically described interms of resource blocks, where a resource block corresponds to one slot(0.5 ms) in the time domain and 12 subcarriers in the frequency domain.Resource blocks are numbered in the frequency domain, starting with 0from one end of the system bandwidth.

Downlink transmissions are dynamically scheduled, i.e., in each subframethe base station transmits control information about to which userequipments data is transmitted and upon which resource blocks the datais transmitted, in the current downlink subframe. This control signalingis typically transmitted in the first 1, 2, 3 or 4 OFDM symbols in eachsubframe. A downlink system with 3 OFDM symbols for control purposes isillustrated in FIG. 3. The dynamic scheduling information iscommunicated to the user equipments via a Physical Downlink ControlChannel (PDCCH) transmitted in the control region. After successfuldecoding of a PDCCH, the user equipment shall perform reception of thePhysical Downlink Shared Channel (PDSCH) or transmission of the PhysicalUplink Shared Channel (PUSCH) according to pre-determined timingspecified in the LTE specifications.

LTE uses a Hybrid-Automatic Repeat Request (HARQ), where, afterreceiving downlink data in a subframe, the user equipment attempts todecode it and reports to the base station whether the decoding wassuccessful, sending an Acknowledge (ACK), or not, sending aNon-Acknowledgement (NACK) via the Physical Uplink Control CHannel(PUCCH). In case of an unsuccessful decoding attempt, the base stationmay retransmit the erroneous data. Similarly, the base station mayindicate to the UE whether the decoding of the PUSCH was successful,sending an ACK, or not, sending a NACK, via the Physical Hybrid ARQIndicator CHannel (PHICH).

Uplink control signaling from the user equipment to the base station maycomprise (1) HARQ acknowledgements for received downlink data; (2) userequipment reports related to the downlink channel conditions, used asassistance for the downlink scheduling; and/or (3) scheduling requests,indicating that a mobile user equipment needs uplink resources foruplink data transmissions.

If the mobile user equipment has not been assigned an uplink resourcefor data transmission, the L1/L2 control information, such aschannel-status reports, HARQ acknowledgments, and scheduling requests,is transmitted in uplink resources e.g. in resource blocks, specificallyassigned for uplink L1/L2 control on Release 8 (Rel-8) PUCCH. Asillustrated in FIG. 4, these uplink resources are located at the edgesof the total available transmission bandwidth. Each such uplink resourcecomprises 12 “subcarriers” (one resource block) within each of the twoslots of an uplink subframe. In order to provide frequency diversity,these frequency resources are frequency hopping, indicated by the arrow,on the slot boundary, i.e. one “resource” comprises 12 subcarriers atthe upper part of the spectrum within the first slot of a subframe andan equally sized resource at the lower part of the spectrum during thesecond slot of the subframe or vice versa. If more resources are neededfor the uplink L1/L2 control signaling, e.g. in case of very largeoverall transmission bandwidth supporting a large number of users,additional resources blocks may be assigned next to the previouslyassigned resource blocks.

Carrier Aggregation

The LTE Release 10 (Rel-10) standard has recently been standardized,supporting bandwidths larger than 20 MHz. One requirement on LTE Rel-10is to assure backward compatibility with LTE Rel-8. This may alsoinclude spectrum compatibility. That would imply that an LTE Rel-10carrier, wider than 20 MHz, should appear as a number of LTE carriers toan LTE Rel-8 user equipment. Each such carrier may be referred to as aComponent Carrier (CC). In particular for early LTE Rel-10 deploymentsit may be expected that there will be a smaller number of LTERel-10-capable user equipments compared to many LTE legacy userequipments. Therefore, it may be useful to assure an efficient use of awide carrier also for legacy user equipments, i.e. that it is possibleto implement carriers where legacy user equipments may be scheduled inall parts of the wideband LTE Rel-10 carrier. The straightforward way toobtain this would be by means of Carrier Aggregation (CA). CA impliesthat an LTE Rel-10 user equipment may receive multiple CCs, where theCCs have, or at least the possibility to have, the same structure as aRel-8 carrier. CA is illustrated in FIG. 5.

The number of aggregated CCs as well as the bandwidth of the individualCCs may be different for uplink and downlink. A symmetric configurationrefers to the case where the number of CCs in downlink and uplink is thesame whereas an asymmetric configuration refers to the case that thenumber of CCs is different. It should be noted that the number of CCsconfigured in a cell may be different from the number of CCs seen by auser equipment. A user equipment may for example support more downlinkCCs than uplink CCs, even though the network is configured with the samenumber of uplink and downlink CCs.

During an initial access, an LTE Rel-10 user equipment behaves similarlyto a LTE Rel-8 user equipment. Upon successful connection to the networka user equipment may—depending on its own capabilities and thenetwork—be configured with additional CCs for uplink and downlink.Configuration is based on the Radio Resource Control (RRC). Due to theheavy signaling and rather slow speed of RRC signaling it is envisionedthat a user equipment may be configured with multiple CCs even thoughnot all of them are currently used. If a user equipment is configured onmultiple CCs this would imply it has to monitor all downlink CCs forPDCCH and PDSCH. This implies a wider receiver bandwidth, highersampling rates, etc., resulting in high power consumption.

To mitigate the above described problems, LTE Rel-10 supports activationof CCs on top of configuration. The user equipment monitors onlyconfigured and activated CCs for PDCCH and PDSCH. Since activation isbased on Medium Access Control (MAC) control elements, which are fasterthan RRC signaling, activation/de-activation may follow the number ofCCs that are required to fulfill the current data rate needs. Uponarrival of large data amounts multiple CCs are activated, used for datatransmission, and de-activated if not needed anymore. All but one CC,the Downlink (DL) Primary CC (DL PCC), may be de-activated. Therefore,activation provides the possibility to configure multiple CC but onlyactivate them on a need-to basis. Most of the time a user equipmentwould have one or very few CCs activated resulting in a lower receptionbandwidth and thus battery consumption.

Scheduling of a CC may be done on the PDCCH via downlink assignments.Control information on the PDCCH may be formatted as a Downlink ControlInformation (DCI) message. In Rel-8 a user equipment may only operatewith one downlink and one uplink CC. The association between downlinkassignment, uplink grants and the corresponding downlink and uplink CCsis therefore clear. In Rel-10 two modes of CA should be distinguished. Afirst mode is very similar to the operation of multiple Rel-8 CC, adownlink assignment or uplink grant contained in a DCI messagetransmitted on a CC is either valid for the downlink CC itself or forassociated (either via cell-specific or user equipment specific linking)uplink CC. A second mode of operation augments a DCI message with theCarrier Indicator Field (CIF). A DCI comprising a downlink assignmentwith CIF is valid for that downlink CC indicted with CIF and a DCIcomprising an uplink grant with CIF is valid for the indicated uplinkCC.

DCI messages for downlink assignments comprise among others resourceblock assignment, modulation and coding scheme related parameters, HARQredundancy version, etc. In addition to those parameters that relate tothe actual downlink transmission, most DCI formats for downlinkassignments also comprise a bit field for Transmit Power Control (TPC)commands. These TPC commands are used to control the uplink powercontrol behavior of the corresponding PUCCH that is used to transmit theHARQ feedback.

In Rel-10 LTE, the transmission of PUCCH is mapped onto one specificuplink CC, the Uplink (UL) Primary CC (UL PCC). User equipmentsconfigured with a single downlink CC (which is then the DL PCC) anduplink CC (which is then the UL PCC) are operating dynamic ACK/NACK onPUCCH according to Rel-8. The first Control Channel Element (CCE) usedto transmit PDCCH for the downlink assignment determines the dynamicACK/NACK resource on Rel-8 PUCCH. Since only one downlink CC iscell-specifically linked with the UL PCC, no PUCCH collisions may occursince all PDCCH are transmitted using different first CCE.

Upon reception of downlink assignments on a single Secondary CC (SCC) orreception of multiple DL assignments, CA PUCCH should be used. Adownlink SCC assignment alone is untypical. The scheduler in the basestation should strive to schedule a single downlink CC assignment on theDL PCC and try to de-activate SCCs if not needed. A possible scenariothat may occur is that the base station schedules user equipment onmultiple downlink CCs including the PCC. If the user equipment missesall but the DL PCC assignment it will use Rel-8 PUCCH instead of CAPUCCH. To detect this error case the base station has to monitor boththe Rel-8 PUCCH and the CA PUCCH.

In Rel-10 LTE, the CA PUCCH format is based on the number of configuredCCs. Configuration of CCs is based on RRC signaling. After successfulreception/application of the new configuration a confirmation message issent back making RRC signaling very safe.

Time Division Duplex

Transmission and reception from a node, e.g. user equipment in acellular system such as LTE, may be multiplexed in the frequency domainor in the time domain (or combinations thereof). Frequency DivisionDuplex (FDD) as illustrated to the left in FIG. 6 implies that downlinkand uplink transmissions take place in different, sufficientlyseparated, frequency bands. Time Division Duplex (TDD), as illustratedto the right in FIG. 6, implies that downlink and uplink transmissionstake place in different, non-overlapping time slots. Thus, TDD mayoperate in unpaired spectrum, whereas FDD requires paired spectrum.

Typically, the structure of the transmitted signal in a communicationsystem is organized in the form of a frame structure. For example, LTEuses ten equally-sized subframes of length 1 ms per radio frame asillustrated in FIG. 7.

In the case of FDD operation (upper part of FIG. 7), there are twocarrier frequencies, one for uplink transmission (f_(UL)) and one fordownlink transmission (f_(DL)). At least with respect to the userequipment in a cellular communication system, FDD may be either fullduplex or half duplex. In the full duplex case, a user equipment maytransmit and receive simultaneously, while in half-duplex operation, theuser equipment cannot transmit and receive simultaneously (the basestation is capable of simultaneous reception/transmission though, e.g.receiving from one user equipment while simultaneously transmitting toanother user equipment). In LTE, a half-duplex user equipment ismonitoring/receiving in the downlink except when explicitly beinginstructed to transmit in a certain subframe.

In the case of TDD operation (lower part of FIG. 7), there may be only asingle carrier frequency and uplink and downlink transmissions aretypically separated in time on a cell basis. As the same carrierfrequency is used for uplink and downlink transmission, both the basestation and the mobile user equipments need to switch from transmissionto reception and vice versa. An aspect of any TDD system is to providethe possibility for a sufficiently large guard time where neitherdownlink nor uplink transmissions occur. This is required to avoidinterference between uplink and downlink transmissions. For LTE, thisguard time is provided by special subframes (subframe 1 and, in somecases, subframe 6), which are split into three parts: a downlink part, aDownlink Pilot Time Slot (DwPTS), a guard period (GP), and an uplinkpart, an Uplink Pilot Time Slot (UpPTS). The remaining subframes areeither allocated to uplink or downlink transmission.

SUMMARY

An object of some of the example embodiments presented herein is toprovide an efficient means of assigning uplink-downlink configurationsacross all aggregated CCs. Accordingly, some of the example embodimentsmay be directed towards a method, in a base station, for configuringcontrol timing to and from a user equipment in a multiple cellcommunications network. The method comprises determining at least onetiming configuration number for a plurality of aggregated cells of themultiple cell communications network. Each aggregated cell is associatedwith an uplink-downlink configuration number, where at least twouplink-downlink configuration numbers of the plurality of aggregatedcells are not equal. The plurality of aggregated cells is associatedwith the user equipment. The method also comprises assigning the atleast one timing configuration number to the user equipment.

Some of the example embodiments may be directed towards a base stationfor configuring control timing to and from a user equipment in amultiple cell communications network. The base station comprises adetermination unit configured to determine at least one timingconfiguration number for a plurality of aggregated cells of the multiplecell communications network. Each aggregated cell is associated with anuplink-downlink configuration number. At least two uplink-downlinkconfiguration numbers of the plurality of aggregated cells are notequal. The plurality of aggregated cells is associated with the userequipment. The base station also comprises an assignment unit configuredto assign the at least one timing configuration number to the userequipment.

Some of the example embodiments may be directed towards a method, in auser equipment, for a configuration of control timing for a userequipment in a multiple cell communications network. The methodcomprises receiving, from a base station, at least one timingconfiguration number for a plurality of aggregated cells of the multiplecell communications network. Each aggregated cell is associated with anuplink-downlink configuration number, and where at least twouplink-downlink configuration numbers of the plurality of aggregatedcells are not equal. The plurality of aggregated cells is associatedwith the user equipment. The method also comprises implementing controltiming based on the at least one timing configuration number.

Some of the example embodiments may be directed towards a userequipment, for a configuration of control timing for a user equipment ina multiple cell communications network. The user equipment comprises adetermining unit configured to receive, from a base station, at leastone timing configuration number for a plurality of aggregated cells ofthe multiple cell communications network, where each aggregated cell isassociated with an uplink-downlink configuration number, and where atleast two uplink-downlink configuration numbers of the plurality ofaggregated cells are not equal. The plurality of aggregated cells isassociated with the user equipment. The user equipment also comprises animplementation unit configured to implement control timing based on theat least one timing configuration number.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of the example embodiments, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe example embodiments.

FIG. 1 is an illustrative example of a LTE downlink physical resource;

FIG. 2 is a schematic of a LTE time-domain structure;

FIG. 3 is an illustration of a downlink subframe;

FIG. 4 is an illustrative example of an uplink L1/L2 control signallingtransmission on Rel-8 PUCCH;

FIG. 5 is an illustrative example of carrier aggregation;

FIG. 6 is an illustrative example of frequency and time-division duplex;

FIG. 7 is a schematic of an uplink-downlink time/frequency structure forLTE for the case of FDD and TDD;

FIG. 8 is a schematic of different downlink/uplink configurations forthe case of TDD;

FIG. 9 is an illustrative example of uplink-downlink interference inTDD;

FIG. 10 is an illustration of PDSCH A/N feedback timings for aconfiguration 1 cell and a configuration 2 cell;

FIG. 11 is an illustration of PUSCH grant and A/N feedback timings for aconfiguration 1 cell and a configuration 2 cell;

FIG. 12 is an illustration of PDSCH A/N feedback timings for aconfiguration 1 cell and a configuration 3 cell;

FIG. 13 is an illustration of PUSCH grant and A/N feedback timings for aconfiguration 1 cell and a configuration 3 cell;

FIG. 14 is an illustrative example of carrier aggregation of TDD cellswith different uplink-downlink configurations;

FIG. 15 is an illustrative example of subframe compatibility hierarchy,according to some of the example embodiments;

FIG. 16 is an illustration of PUSCH grant and A/N feedback timings foraggregation of a configuration 1 cell as Pcell and a configuration 2cell as Scell, according to some of the example embodiments;

FIG. 17 is an illustration of PUSCH grant and A/N feedback timings foraggregation of a configuration 2 cell as Pcell and a configuration 1cell as Scell, according to some of the example embodiments;

FIG. 18 is an illustration of PDSCH A/N feedback timings for aggregationof a configuration 1 cell and a configuration 2 cell, according to someof the example embodiments;

FIG. 19 is an illustration of PUSCH grant and A/N feedback timings foraggregation of a configuration 1 cell as Pcell and a configuration 3cell as Scell, according to some of the example embodiments;

FIG. 20 is an illustration of PUSCH grant and A/N feedback timings foraggregation of a configuration 3 cell as Pcell and a configuration 1cell as Scell, according to some of the example embodiments;

FIG. 21 is an illustration of PDSCH A/N feedback timings for aggregationof a configuration 1 cell and a configuration 3 cell, according to someof the example embodiments;

FIG. 22 is an illustrative example of the timing of additionalforward-subframe DL scheduling PDCCHs in support of half-duplex UEs withaggregation of a configuration 1 cell and a configuration 2 cell,according to some of the example embodiments;

FIG. 23 is an illustrative example of the timing of additionalforward-subframe DL scheduling PDCCHs in support of half-duplex UEs withaggregation of a configuration 1 cell and a configuration 3 cell,according to some of the example embodiments;

FIG. 24 is an illustrative example of the timing of additionalcross-carrier forward-subframe DL scheduling PDCCHs in support offull-duplex UEs with aggregation of a configuration 1 cell as Pcell anda configuration 2 cell as Scell, according to some of the exampleembodiments;

FIG. 25 is an illustrative example of the timing of additionalcross-carrier forward-subframe DL scheduling PDCCHs in support offull-duplex UEs with aggregation of a configuration 1 cell and aconfiguration 3 cell, according to some of the example embodiments;

FIG. 26 is a schematic of a network node configured to perform theexample embodiments described herein;

FIG. 27 is a flow diagram depicting example operations of the networknode of FIG. 26.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as particularcomponents, elements, techniques, etc. in order to provide a thoroughunderstanding of the example embodiments. However, the exampleembodiments may be practiced in other manners that depart from thesespecific details. In other instances, detailed descriptions ofwell-known methods and elements are omitted so as not to obscure thedescription of the example embodiments.

As part of the development of the example embodiments presented herein,a problem will first be identified and discussed. TDD allows fordifferent asymmetries in terms of the amount of resources allocated foruplink and downlink transmission, respectively, by means of differentdownlink/uplink configurations. In LTE, there are seven differentconfigurations as shown in FIG. 8. Note that in the description below,under the heading ‘TDD HARQ Timing’, a downlink subframe may mean eitherdownlink or the special subframe.

To avoid severe interference between downlink and uplink transmissionsbetween different cells, neighbor cells should have the samedownlink/uplink configuration. If this is not done, uplink transmissionin one cell may interfere with downlink transmission in the neighboringcell and vice versa as illustrated in FIG. 9. Hence, the downlink/uplinkasymmetry may typically not vary between cells, but is signaled as partof the system information and remains fixed for a long period of time.

The description provided herein is arranged as follows. First, anoverview of current systems and methods for control timing configurationis presented under the heading ‘Existing Systems—TDD HARQ ControlTiming’. Thereafter, limitations of the existing systems are exploredunder the subheading ‘Problems with Existing Solutions’.

A basis for the example embodiments is thereafter presented in thesection entitled ‘Subframe Timing Compatibility’, where complexconfiguration tables (explained in ‘Existing Systems—TDD HARQ ControlTiming’) may be replaced with the use of a subframe timing compatibilityhierarchy. Thereafter, examples of control timing configurationassignment, utilizing the subframe timing compatibility hierarchy, areprovided in the sub-section entitled ‘Configuration Assignment’.Examples of control timing configuration assignment based on an orderedlisting of the subframe timing compatibility hierarchy is provided inthe sub-section ‘Computation of the Subframe Timing Compatibility basedon Efficient Storage.’

Thereafter, examples of control timing configuration assignment of userequipments utilizing a half-duplex mode of operation are provided in thesub-section ‘Examples of Half-Duplex Configuration Assignment’.Similarly, examples of control timing configuration assignment of userequipments utilizing a full-duplex mode of operation are provided in thesub-section ‘Examples of Full-Duplex Configuration Assignment’.Thereafter examples of forward downlink scheduling with respect to userequipments with full and half-duplex modes of operation is providedunder the sub-heading ‘Examples of Forward Downlink Scheduling’.

Finally, examples of network node configurations and example operationsof such nodes are presented under the sub-headings ‘Example NodeConfigurations’ and ‘Example Node Operations’. It should be appreciatedthat the example node operations provide a generalized explanation ofnode operations which may encompass all of the examples provided in theforegoing sub-headings which are not related to existing systems.

Existing Systems—TDD HARQ Control Timing

The timings for HARQ ACK/NACK (A/N) feedbacks for the PUSCH and thePDSCH as well as the grant of PUSCH may be specified with extensivetables and procedure descriptions for each uplink-downlinkconfiguration.

For TDD UL/DL (U/D) configurations 1-6 and normal HARQ operation, theuser equipment shall upon detection of a PDCCH with an uplink DCI formatand/or a PHICH transmission in subframe n intended for the userequipment, adjust the corresponding PUSCH transmission in subframe n+k,with k given in Table 1, shown below, according to the PDCCH and PHICHinformation.

TABLE 1 PUSCH grant timing k for TDD configurations 0-6 TDD U/D subframenumber n Configuration 0 1 2 3 4 5 6 7 8 9 0 4 6 4 6 1 6 4 6 4 2 4 4 3 44 4 4 4 4 5 4 6 7 7 7 7 5

For TDD U/D configuration 0 and normal HARQ operation the user equipmentshall upon detection of a PDCCH with uplink DCI format and/or a PHICHtransmission in subframe n intended for the user equipment, adjust thecorresponding PUSCH transmission in subframe n+k if the Most SignificantBit (MSB) of the UL index in the PDCCH with uplink DCI format is set to1 or PHICH is received in subframe n=0 or 5 in the resourcecorresponding to I_(PHICH)=0, with k given in Table 1. If, for TDD U/Dconfiguration 0 and normal HARQ operation, the Least Significant Bit(LSB) of the UL index in the DCI format 0/4 is set to 1 in subframe n ora PHICH is received in subframe n=0 or 5 in the resource correspondingto I_(PHICH)=1, or PHICH is received in subframe n=1 or 6, the userequipment shall adjust the corresponding PUSCH transmission in subframen+7. If, for TDD U/D configuration 0, both the MSB and LSB of the ULindex in the PDCCH with uplink DCI format are sent in subframe n, theuser equipment shall adjust the corresponding PUSCH transmission in bothsubframes n+k and n+7, with k given in Table 1.

For PUSCH transmissions scheduled from a serving cell c in subframe n, auser equipment shall determine the corresponding PHICH resource ofserving cell c in subframe n+k_(PHICH), where k_(PHICH) is given inTable 2, provided below, for TDD. For subframe bundling operation, thecorresponding PHICH resource is associated with the last subframe in thebundle.

TABLE 2 _(k) _(PHICH) for TDD TDD U/D subframe index n Configuration 0 12 3 4 5 6 7 8 9 0 4 7 6 4 7 6 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 4 6 64 7

The user equipment shall also feedback PDSCH decoding A/N information inpre-defined UL subframes. The user equipment shall transmit such a HARQA/N response on the PUCCH in UL subframe, if there is PDSCH transmissionindicated by the detection of corresponding PDCCH or there is PDCCHindicating downlink SPS release within subframe(s) n−k, where k iswithin the association set K={k₀, k₁, . . . k_(M−1)} listed in Table 3,provided below.

TABLE 3 Downlink association set index _(K): {k₀, k₁, . . . k_(M−1)} forTDD UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 6 4 6 4 1 7, 64 7, 6 4 2 8, 7, 4, 6 8, 7, 4, 6 3 7, 6, 11 6, 5 5, 4 4 12, 8, 7, 11 6,5, 4, 7 5 13, 12, 9, 8, 7, 5, 4, 11, 6 6 7 7 5 7 7

In LTE Rel-10, all HARQ control timings are determined based on thePrimary-cell (Pcell) configuration number as discussed above. Thedetermination of HARQ operations in LTE Rel-10 work only if allaggregated TDD cells have an identical U/D configuration. However, whendeveloping the example embodiments presented herein it has beendiscovered that a straightforward extension of this operation foraggregation of different U/D configurations proves difficult.

Consider the PDSCH A/N feedback timing example for aggregating aconfiguration 1 cell and a configuration 2 cell illustrated in FIG. 10.In FIG. 10, U represents uplink subframes, D represents downlinksubframes, and S represents special subframes which may be used for bothuplink and downlink. It should be appreciated that for the purpose ofsimplicity, the S subframes will be treated as downlink subframes in theexamples provided herein.

If the configuration 2 cell is the Pcell, A/N feedback for theconfiguration 1 Secondary-cell (Scell) PDSCH may be fed-back based onthe timing rules of Pcell. However, if the configuration 1 cell is thePcell, there will be no A/N feedback timing rules for subframes 3 and 8in the configuration 2 Scell.

Consider the PUSCH grant and A/N feedback timing example for aggregatinga configuration 1 cell and a configuration 2 cell illustrated in FIG.11. If the configuration 1 cell is the Pcell, PUSCH grant and A/Nfeedback for the configuration 2 Scell may be fed-back based on thetiming rules of Pcell. However, if the configuration 2 cell is thePcell, PUSCH cannot be scheduled for subframe 3 and 8 in configuration 1Scell because there is no such UL grant timing in configuration 2. Notethat A/N feedback timing rules for these two subframes are notavailable, either.

The control timing problems may be even more severe than the examplesdiscussed above. In the case of aggregating a configuration 1 and aconfiguration 3 cells, the HARQ control timings don't work regardless ofwhich configuration is the Pcell.

More specifically, consider the PDSCH A/N feedback timing illustrated inFIG. 12:

-   -   If configuration 1 is the Pcell, PDSCH A/N for subframes 7 & 8        of the configuration 3 Scell cannot be fed back.    -   If configuration 3 is the Pcell, PDSCH A/N for subframe 4 of the        configuration 1 Scell cannot be fed back.

Further, consider the PUSCH grant and A/N feedback timing illustrated inFIG. 13:

-   -   If configuration 1 is the Pcell, PUSCH for subframe 4 in        configuration 3 Scell cannot be scheduled.    -   If configuration 3 is the Pcell, PUSCH for subframe 7 & 8 in        configuration 1 Scell cannot be scheduled.        Problems with Existing Systems

The following are examples of some of the problems with existingsolutions, which have been recognized when developing the embodimentspresented herein. In Rel-10, carrier aggregation of TDD cells isspecified with the restriction that the U/D configurations for all theaggregated cells are identical. There is a need to allow more flexiblecarrier aggregation of TDD cells is to be addressed in Rel-11 of LTE.

As discussed above, the U/D configurations of neighboring cells need tobe compatible to avoid severe interference problems. However, there arecases where the neighboring cells are operated by different operators ordifferent wireless systems. The LTE TDD cells adjacent to thoseneighboring systems are hence required to adopt certain compatible U/Dconfigurations. As a result, an operator may have several TDD cellshaving different U/D configurations on different frequencies asillustrated in FIG. 14.

A further complication from such aggregation cases is that the nominallyTDD user equipment may be required to transmit and receivesimultaneously in certain subframes (such as subframe 7 and 8 in FIG.14). Such FDD-like operations are incompatible with existing designs ofTDD user equipments. To enable such full-duplex operations in Rel-11 mayimpose additional user equipment complexity and costs. It is thereforenecessary to also consider possible half-duplex operations during suchconflicting subframes. That is, the user equipment should be instructedto perform either reception or transmission but not both during suchconflicting subframes.

To circumvent problems such those identified in the above, addingadditional HARQ control timing rules based on specific aggregation casesmay be performed. In additional to the existing timing rules for sevenTDD configurations,

$\begin{pmatrix}7 \\2\end{pmatrix} = 21$additional sets of rules may be added to specify the HARQ behaviors forevery possible pair of heterogeneous configuration. On top of these,additional specification for aggregation of three different U/Dconfigurations may also be introduced. Apparently, specifying theseadditional rules for supporting aggregation of different U/Dconfigurations will substantially increase the LTE complexity andimplementation costs.Subframe Timing Compatibility

To enable a systematic solution to a plurality of aggregation scenarioswith different TDD U/D configurations, according to some of the exampleembodiments, a subframe timing compatibility is designed and illustratedin FIG. 15. The subframe timing compatibility is a hierarchy that may beencoded as look-up tables, a linked list or a plurality of digitalrepresentations suitable for storage in communication devices.

The subframe timing compatibility hierarchy may be designed with thefollowing principles:

(1) The UL subframes in a TDD configuration are also UL subframes inthose TDD configurations that may be corrected with upward arrows.

For example, subframes 2 and 3 are UL subframes in configuration 4.These two subframes are also UL in configurations 3, 1, 6 and 0, all ofwhich may be connected from configuration 4 with upward arrows. As asecond example, subframes 2 and 7 are UL subframes in configuration 2.These two subframes are not both UL in configuration 3 because there isno upward arrow connecting the two configurations.

(2) The DL subframes in a TDD configuration are also DL subframes inthose TDD configurations that may be corrected with downward arrows.

For example, subframe 0, 1, 5, 6 and 9 are DL subframes in configuration6. These five subframes are also DL in configurations 1, 2, 3, 4 and 5,all of which may be connected from configuration 6 with downward arrows.As a second example, subframe 7 is a DL subframe in configuration 3 butnot a DL subframe in configuration 2 because there is no downward arrowconnecting the two configurations.

With these design properties, the subframe timing compatibilityhierarchy may provide the following utility:

(1) Given a set of TDD configurations to be aggregated, a TDDconfiguration that may be connected from all of the given TDDconfigurations with upward arrows has the following two properties:

-   -   The TDD configuration comprises UL subframes that are a superset        of all UL subframes from all given TDD configurations.    -   The TDD configuration comprises DL subframes that are available        in all given TDD configurations.        Example One

Given TDD configuration 1 and 2, all subframes that are UL in eitherconfiguration 1 or 2 are also UL subframes in configuration 1, 6 and 0.The DL subframes in configuration 1, 6 or 0 are also DL subframes inconfiguration 1 and 2.

Given TDD configuration 1 and 3, all subframes that are UL in eitherconfiguration 1 or 3 are also UL in configuration 6 and 0. The DLsubframes in configuration 6 or 0 are also DL subframes in configuration1, 2, 3, 4, 5 and 6.

Given TDD configuration 2, 3 and 4, all subframes that are UL in any ofthe three configurations are also UL in configuration 6 and 0. The DLsubframes in configuration 6 or 0 are also DL subframes in configuration1, 2, 3, 4, 5 and 6.

Given a set of TDD configurations, a TDD configuration that may beconnected from all of the given TDD configurations with downward arrowshas the following two properties:

-   -   The TDD configuration comprises DL subframes that are a superset        of all DL subframes from all given TDD configurations.    -   The TDD configuration comprises UL subframes that are available        in all given TDD configurations.        Example Two

Given TDD configuration 1 and 2, all subframes that are DL in eitherconfiguration 1 or 2 are also DL in configuration 2 and 5. The ULsubframes in configuration 2 or 5 are also UL subframes in configuration1, 2, 6 and 0.

Given TDD configuration 1 and 3, all subframes that are DL in eitherconfiguration 1 or 3 are also DL in configuration 4 and 5. The ULsubframes in configuration 4 or 5 are also UL subframes in configuration0, 3, 4 and 6.

Given TDD configuration 2, 3 and 4, all subframes that are DL in any ofthe three configurations are also DL in configuration 5. The ULsubframes in configuration 5 are also UL subframes in configuration 0,1, 2, 3, 4 and 6.

Configuration Assignment

In Rel-8 TDD, the following two sets of subframe timings are set basedon the same parameter, which is the serving cell U/D configurationnumber: (1) UL HARQ control and grant subframe timing, and (2) DL HARQA/N subframe timing. In Rel-10 TDD CA, both types of subframe timingsacross all cells are set based on the same parameter, which is thePcellU/D configuration number.

To support carrier aggregation of TDD cells with different U/Dconfigurations, the user equipment may be configured with the followingtwo numbers according to the teaching of the example embodiments: (1) anUL control timing configuration number for setting UL HARQ and granttimings across all aggregated cells, and (2) a DL HARQ control timingconfiguration number for setting DL HARQ timings across all aggregatedcells.

The UL control timing configuration number may be set to theconfiguration number of a configuration that may be connected from allaggregated configurations with upward arrows in the subframe timingcompatibility hierarchy in FIG. 15. If more than one configurationnumber may be chosen, the chosen setting may be the configuration at thelowest level in the subframe timing compatibility hierarchy. The chosensetting may result in more DL subframes for PUSCH grant and A/Nfeedback. The following example cases are provided below for the purposeof explaining some of the example embodiments.

Example Case 1:

If cells with configuration 1 and 2 are aggregated, the UL controltiming configuration number may be set to 1, 6 or 0. The chosen settingmay be 1.

Example Case 2:

If cells with configuration 1 and 3 are aggregated, the UL controltiming configuration number may be set to 6 or 0. The chosen setting maybe 6, which is different than the U/D configuration numbers of the twoTDD cells.

This UL control timing configuration number setting ensures identicalPUSCH grant and PHICH timings across all CCs and DL subframes areavailable at these timings regardless of the Pcell configuration. Thatis, the PUSCH grant and PHICH subframes are never in subframes withconflicting U/D directions across different CCs. This setting furtherensures all UL subframes from all aggregated CCs may be scheduled eitherin-CC or cross-CC.

The DL HARQ control timing configuration number may be set to theconfiguration number of a configuration that may be connected from allaggregated configurations with downward arrows in the subframe timingcompatibility hierarchy in FIG. 15. If more than one configurationnumber may be chosen, the chosen setting may be that of theconfiguration at the highest level in the subframe timing compatibilityhierarchy. The chosen setting may result in more UL subframes for PDSCHA/N feedback. The following example cases are provided below for thepurpose of explaining some of the example embodiments.

Example Case 1:

If cells with configuration 1 and 2 are aggregated, the DL HARQ controltiming configuration number may be set to 2 or 5. The chosen setting maybe 2.

Example Case 2:

If cells with configuration 1 and 3 are aggregated, the DL HARQ controltiming configuration number may be set to 4 or 5. The chosen setting maybe 4, which is different than the U/D configuration numbers of the twoTDD cells.

This DL HARQ control timing configuration number setting ensuresidentical PDSCH A/N feedback timings across all CCs and UL subframes areavailable at these timings regardless of the Pcell configuration.

Example Carrier Aggregation of Configuration 1 and 2 TDD Cells

To support the aggregation of configuration 1 and 2 TDD cells, the twoHARQ control timing configuration numbers may be set as follows:

-   -   The UL control timing configuration number may be set to 1.    -   The DL HARQ control timing configuration number may be set to 2.

Note these configuration number settings are applicable regardless ofwhich of the two TDD cells serves as the Pcell.

The PUSCH grant and A/N feedback timings for aggregation of aconfiguration 1 cell as Pcell and a configuration 2 cell as Scell areillustrated in FIG. 16. The PUSCH grant and A/N feedback timings foraggregation of a configuration 2 cell as Pcell and a configuration 1cell as Scell are illustrated in FIG. 17. This analysis shows that allthe UL subframes may be scheduled either from the Pcell (ifcross-carrier scheduling is configured) or from the Scell itself (ifcross-carrier scheduling is not configured). Furthermore, A/N feedbacktimings for all UL subframes are clearly assigned.

The PDSCH A/N feedback timings for aggregation of a configuration 1 celland a configuration 2 cell is shown in FIG. 18. The analysis confirmsthat A/N feedbacks for all PDSCH in both the Pcell and the Scell areclearly assigned to suitable UL subframes on the Pcell.

Example Carrier Aggregation of Configuration 1 and 3 TDD Cells

To support the aggregation of configuration 1 and 3 TDD cells, the twoHARQ control timing configuration numbers may be set as follows:

-   -   The UL control timing configuration number may be set to 6.    -   The DL HARQ control timing configuration number may be set to 4.

Note these configuration number settings are applicable regardless ofwhich of the two TDD cells serves as the Pcell.

The PUSCH grant and A/N feedback timings (i.e., for uplink A/N feedbacktiming) for aggregation of a configuration 1 cell as Pcell and aconfiguration 3 cell as Scell are illustrated in FIG. 19. The PUSCHgrant and A/N feedback timings for aggregation of a configuration 3 cellas Pcell and a configuration 1 cell as Scell are illustrated in FIG. 20.This analysis shows that all the UL subframes may be scheduled eitherfrom the Pcell (if cross-carrier scheduling is configured) or from theScell itself (if cross-carrier scheduling is not configured).Furthermore, A/N feedback timings for all UL subframes are clearlyassigned.

The PDSCH A/N feedback timings for aggregation of a configuration 1 celland a configuration 3 cell is shown in FIG. 21. The analysis confirmsthat A/N feedbacks for all PDSCH in both the Pcell and the Scell areclearly assigned to suitable UL subframes on the Pcell.

Computation of the Subframe Timing Compatibility Based on EfficientStorage

As should be appreciated from above, according to some of the exampleembodiments, for a given set of aggregated TDD cells with different U/Dconfigurations, the UL control and DL HARQ control timing configurationnumbers may be set based on a systematic rule encoded in the subframetiming compatibility hierarchy, for example as illustrated in FIG. 15.The UL control and DL HARQ control timing configuration numbers sochosen may be different than any of the U/D configuration number of theaggregated cells.

The UL control timing configuration number may be set to theconfiguration number of a configuration that may be connected from allaggregated configurations with upward arrows in the subframe timingcompatibility hierarchy in FIG. 15. If more than one configurationnumber may be chosen, a setting may be chosen to be the configuration atthe lowest level in the subframe compatibility hierarchy. This settingresults in more DL subframes for PUSCH grant and A/N feedback.

The DL HARQ control timing configuration number may be set to theconfiguration number of a configuration that may be connected from allaggregated configurations with downward arrows in the subframe timingcompatibility hierarchy in FIG. 15. If more than one configurationnumber may be chosen, the setting may be chosen to be the configurationat the highest level in the subframe timing compatibility hierarchy.This setting results in more UL subframes for PDSCH A/N feedback.

Some of the example embodiments may also be directed towards efficientdigital representation and storage methods of the subframe timingcompatibility hierarchy. Some of the example embodiments may also bedirected towards efficient computational methods and a correspondingapparatus for computing the UL control timing configuration number andthe DL HARQ control timing configuration number.

According to some of the example embodiments, the subframe timingcompatibility hierarchy may be represented with a table of sets. The ULcontrol timing configuration number and the DL HARQ control timingconfiguration number may be computed with set intersection operations.If there is more than one control timing configuration number candidatesafter the set intersection operations, the network node may select apreferred control timing configuration number setting based on at leastsystem loads and user equipment application needs.

An UL control timing configuration candidate set and a DL HARQ controltiming configuration candidate set may be stored for each of the LTEcell U/D configurations. An example of the specific values of thecandidate sets are shown in the table provided below.

TABLE 4 Control Timing Configuration Sets Component UL control timing DLHARQ control cell U/D configuration timing configuration configurationcandidate set candidate set 0 {0} {0,6,1,3,2,4,5} 1 {1,6,0} {1,2,4,5} 2{2,1,6,0} {2,5} 3 {3,6,0} {3,4,5} 4 {4,1,3,6,0} {4,5} 5 {5,2,4,1,3,6,0}{5} 6 {6,0} {6,1,3,2,4,5}

According to some of the example embodiments, for a given set of cellU/D configurations to be aggregated, the UL control timing configurationnumber may be set to a configuration number from the intersection of allUL control timing configuration candidate sets corresponding to the cellU/D configurations to be aggregated. The following example cases areprovided below for the purpose of explaining some of the exampleembodiments.

Example Case 1:

If cells with configuration 1 and 2 are aggregated, the corresponding ULcontrol timing configuration candidate sets may be {1,6,0} and{2,1,6,0}. The intersection of all these sets may be computed to be{1,6,0}. Therefore, the UL control timing configuration number may beset to 1, 6 or 0.

Example Case 2:

If cells with configuration 1 and 3 are aggregated, the corresponding ULcontrol timing configuration candidate sets may be {1,6,0} and {3,6,0}.The intersection of all these set may be computed to be {6,0}.Therefore, the UL control timing configuration number may be set to 6 or0.

Example Case 3:

If cells with configuration 1, 3 and 4 are aggregated, the correspondingUL control timing configuration candidate sets may be {1,6,0}, {3,6,0}and {4,1,3,6,0}. The intersection of all these set may be computed to be{6,0}. Therefore, the UL control timing configuration number may be setto 6 or 0.

According to some of the example embodiments, for a given set of cellU/D configurations to be aggregated, the DL HARQ control timingconfiguration number may be set to a configuration number from theintersection of all DL HARQ control timing configuration candidate setscorresponding to the cell U/D configurations to be aggregated. Thefollowing example cases are provided below for the purpose of explainingsome of the example embodiments.

Example Case 1:

If cells with configuration 1 and 2 are aggregated, the corresponding DLHARQ control timing configuration candidate sets may be {1,2,4,5} and{2,5}. The intersection of all these sets may be computed to be {2,5}.Therefore, the DL HARQ control timing configuration number may be set to2 or 5.

Example Case 2:

If cells with configuration 1 and 3 are aggregated, the corresponding DLHARQ control timing configuration candidate sets may be {1,2,4,5} and{3,4,5}. The intersection of all these sets may be computed to be {4,5}.Therefore, the DL HARQ control timing configuration number may be set to4 or 5.

Example Case 3:

If cells with configuration 1, 3 and 4 are aggregated, the correspondingDL HARQ control timing configuration candidate sets may be {1,2,4,5},{3,4,5} and {4,5}. The intersection of all of these sets may be computedto be {4,5}. Therefore, the DL HARQ control timing configuration numbermay be set to 4 or 5.

If there are more than one control timing configuration numbercandidates after the set intersection operations, the network node oruser equipment may select and signal a preferred control timingconfiguration number setting based on at least system loads and userequipment application needs. Signaling of the control timing could forexample be done with radio resource control (RRC) signaling.

It should also be appreciated that, according to some of the exampleembodiments, the subframe timing compatibility hierarchy may berepresented with a table of ordered sets. The UL control timingconfiguration number and the DL HARQ control timing configuration numbermay be computed with set intersection operations while preserving theorder of numbers within the set. The chosen control timing configurationnumber may be the first or last number after the set intersectionoperation.

An UL control timing configuration candidate set and a DL HARQ controltiming configuration candidate set may be stored for each of the LTEcell U/D configurations. The specific values of the candidate or orderedsets are shown in table 4. The order of candidate configuration numbersin each of the candidate sets shown in the table may be preserved instorage.

For a given set of cell U/D configurations to be aggregated, the ULcontrol timing configuration number may be set to a configuration numberfrom the intersection of all UL control timing configuration candidatesets corresponding to the cell U/D configurations to be aggregated,where the set intersection operations preserve the ordering of numbersin the concerned sets. The following example cases are provided belowfor the purpose of explaining some of the example embodiments.

Example 1

If cells with configuration 1 and 2 are aggregated, the corresponding ULcontrol timing configuration candidate or ordered sets may be {1,6,0}and {2,1,6,0}. The intersection of all these set may be computed to be{1,6,0}. Therefore, the chosen UL control timing configuration numbermay be 1.

Example 2

If cells with configuration 1 and 3 are aggregated, the corresponding ULcontrol timing configuration candidate or ordered sets may be {1,6,0}and {3,6,0}. The intersection of all these set may be computed to be{6,0}. Therefore, the chosen UL control timing configuration number maybe 6.

Example 3

If cells with configuration cells 1, 3 and 4 are aggregated, thecorresponding UL control timing configuration candidate or ordered setsmay be {1,6,0}, {3,6,0} and {4,1,3,6,0}. The intersection of all theseset may be computed to be {6,0}. Therefore, the chosen UL control timingconfiguration number may be 6.

For a given set of cell U/D configurations to be aggregated, the DL HARQcontrol timing configuration number may be set to a configuration numberfrom the intersection of all DL HARQ control timing configurationcandidate sets corresponding to the cell U/D configurations to beaggregated, where the set intersection operations preserve the orderingof numbers in the concerned sets. The following example cases areprovided below for the purpose of explaining some of the exampleembodiments.

Example 1

If cells with configuration 1 and 2 are aggregated, the corresponding DLHARQ control timing configuration candidate or ordered sets may be{1,2,4,5} and {2,5}. The intersection of all these set may be computedto be {2,5}. Therefore, the chosen DL HARQ control timing configurationnumber may be 2.

Example 2

If cells with configuration 1 and 3 are aggregated, the corresponding DLHARQ control timing configuration candidate or ordered sets may be{1,2,4,5} and {3,4,5}. The intersection of all these set may be computedto be {4,5}. Therefore, the chosen DL HARQ control timing configurationnumber may be 4.

Example 3

If cells with configuration 1, 3 and 4 are aggregated, the correspondingDL HARQ control timing configuration candidate sets may be {1,2,4,5},{3,4,5} and {4,5}. The intersection of all these set may be computed tobe {4,5}. Therefore, the chosen DL HARQ control timing configurationnumber may be 4.

Examples of Half-Duplex Configuration Assignment

A user equipment capable of only half-duplex operations may performeither transmission or reception in a subframe but not both actions.Therefore, according to some of the example embodiments, subframeswithout conflicting U/D directions may be scheduled with PDCCHtransmitted in the same subframe time (in-subframe scheduling).

For subframes with conflicting U/D directions across CCs, thehalf-duplex user equipments need to be informed of the scheduleddirections in advance. Forward-subframe UL scheduling is already used inLTE. However, additional forward-subframe DL scheduling PDCCHs may beneeded.

According to the example embodiments, the following features aredesigned for the forward-subframe DL scheduling PDCCHs:

-   -   If no cross-CC scheduling is configured, additional        forward-subframe DL scheduling PDCCHs for the individual cells        may be added (referred to as in-CC forward-subframe DL        scheduling PDCCHs).    -   If cross-CC scheduling is configured, additional cross-CC        forward-subframe DL scheduling PDCCHs from the Pcell may be        added.    -   The forward-scheduling timing may be based on the UL grant        timing of the same target cell. Other forward-scheduling timing        methods may also be used.    -   The forward-subframe DL scheduling PDCCHs may be implemented        according to the teaching of flexible carrier indicator.        Example Carrier Aggregation of Configuration 1 and 2 TDD Cells:

To support the aggregation of configuration 1 and 2 TDD cells, the twoHARQ control timing configuration numbers may be set as follows:

-   -   The UL control timing configuration number may be set to 1.    -   The DL HARQ control timing configuration number may be set to 2.

For subframes with conflicting U/D directions across CCs, thehalf-duplex user equipments need to be informed of the scheduleddirections in advance. Additional forward-subframe DL scheduling PDCCHsbased on UL grant timings may be introduced as follows:

-   -   If configuration 1 is a Pcell and cross-CC scheduling is        configured, two additional cross-CC forward-subframe DL        scheduling PDCCHs (from the configuration 1 cell) are shown in        FIG. 22.    -   If configuration 2 is a Pcell or if cross-CC scheduling is not        configured, two additional in-CC forward-subframe DL scheduling        PDCCHs (from the configuration 2 cell) are shown in FIG. 22.        Example Carrier Aggregation of Configuration 1 and 3 TDD Cells

To support the aggregation of configuration 1 and 3 TDD cells, the twoHARQ control timing configuration numbers may be set as follows:

-   -   The UL control timing configuration number may be set to 6.    -   The DL HARQ control timing configuration number may be set to 4.

For subframes with conflicting U/D directions across CCs, thehalf-duplex UEs may need to be informed of the scheduled directions inadvance. Additional forward-subframe DL scheduling PDCCHs based on ULgrant timings may be introduced as follows:

-   -   If no cross-CC scheduling is configured, three in-CC        forward-subframe DL scheduling PDCCHs from the Pcell and Scell        may be added as shown in FIG. 23.    -   If cross-CC scheduling is configured, three cross-CC        forward-subframe DL scheduling PDCCHs from the Pcell may be        added as shown in FIG. 23.        Examples of Full-Duplex Configuration Assignment

A full-duplex user equipment may perform transmission and receptionsimultaneously in subframes with conflicting U/D directions acrossdifferent CCs. According to the above teaching of the exampleembodiments, if cross-carrier scheduling is not configured, all DLsubframes may be scheduled in-CC and in-subframe.

If cross-carrier scheduling is configured, in a subframe withoutconflicting directions, the DL subframes in the scheduling cell maycarry the cross-carrier DL scheduling PDCCHs to schedule other DLsubframes of the same subframe time on other cells. Furthermore, in asubframe with conflicting directions, if the scheduling cell is a DLsubframe, PDCCH(s) may be sent from said subframe to schedule other DLsubframes of the same subframe time on other cells. Additionally, in asubframe with conflicting directions, if the scheduling cell is an ULsubframe, PDCCH(s) cannot be sent from said subframe to schedule otherDL subframes of the same subframe time on other cells.

Thus, according to some of the example embodiments, cross-CCforward-subframe DL scheduling PDCCHs from the scheduling cell may beenabled. According to some of the example embodiments, the cross-CCforward-subframe DL scheduling PDCCHs designed in the exampleembodiments directed towards the half-duplex operations are applied tosupport full-duplex operations with certain cross-carrier schedulingscenarios.

Example Carrier Aggregation of Configuration 1 and 2 TDD Cells

To support the aggregation of configuration 1 and 2 TDD cells, the twoHARQ control timing configuration numbers may be set as follows:

-   -   The UL control timing configuration number may be set to 1.    -   The DL HARQ control timing configuration number may be set to 2.

If configuration 2 is the Pcell, all DL subframes may be scheduledin-subframe and in-CC or cross-CC.

If configuration 1 is the Pcell, if cross-CC scheduling is notconfigured, all DL subframes may be scheduled in-CC and in-subframe. Ifcross-scheduling is configured, all DL subframes in the Scell may beCC-scheduled in subframe except subframes 3 and 8. Note these twosubframes are the subframes with conflicting U/D directions. Hence, thehalf-duplex solution may be reused here. The two subframes are scheduledwith forward-subframe scheduling PDCCH based on the UL grant timings ofthese two subframes. The two additional cross-CC forward-subframe DLscheduling PDCCHs are shown in FIG. 24.

Example Carrier Aggregation of Configuration 1 and 3 TDD Cells

To support the aggregation of configuration 1 and 3 TDD cells, the twoHARQ control timing configuration numbers may be set as follows:

-   -   The UL control timing configuration number may be set to 6.    -   The DL HARQ control timing configuration number may be set to 4.

If cross-CC scheduling is not configured, all DL subframes may bescheduled in-CC and in-subframe. If cross-scheduling is configured, allDL subframes in the Scell may be CC-scheduled in-subframe exceptsubframes 7 and 8 in configuration 3 cannot be cross-scheduledin-subframe if configuration 1 is the Pcell. Additionally, subframe 4cannot be cross-scheduled in-subframe if configuration 3 is the Pcell.

Using the half-duplex solution from the example embodiments directedtowards half-duplex scheduling, two (if configuration 1 is the Pcell) orone (if configuration 3 is the Pcell) additional cross-CCforward-subframe DL scheduling PDCCHs based on the corresponding ULgrant timings are used as shown in FIG. 25.

Examples of Forward Downlink Scheduling

The forward-subframe DL scheduling PDCCHs introduced in the exampleembodiments directed to half and full duplex assignment are new featuresand may require implementation complexity to integrate into existingnetwork node hardware and software architecture. There is hence abenefit in reducing the need to rely on such new forward-subframe DLscheduling PDCCHs.

According to some of the example embodiments, the following twooperation rules may be implemented on the user equipment for a subframewith conflicting directions across the aggregated CCs:

In full-duplex operations, a user equipment may monitor PDCCH(s) inscheduling CC(s) with the DL direction (even if the user equipment hasbeen given in advance grant(s) to transmit in CC(s) with the ULdirection).

In half-duplex operations, a user equipment may monitor PDCCH(s) inscheduling CC(s) with the DL direction if the user equipment has notbeen given in advance any grant to transmit in any CC with the ULdirection.

Example Network Node Configuration

FIG. 26 illustrates an example of a network node 400 which mayincorporate some of the example embodiments discussed above. Accordingto some of the example embodiments, the network node may be a basestation, a user equipment or a relay node. As shown in FIG. 26, node 400may comprise a receiver 407 and transmitter 408 units configured toreceive and transmit, respectively, any form of communications orcontrol signals within a network. It should be appreciated that thereceiver 407 and transmitter 408 units may be comprised as a singletransceiving unit or transceiver circuitry. It should further beappreciated that the receiver 407 and transmitter 408 units, ortransceiving unit, may be in the form of any input/output communicationsport known in the art.

The network node 400 may further comprise at least one memory unit 409that may be in communication with the receiver 407 and transmitter 408units. The memory unit 409 may be configured to store received ortransmitted data and/or executable program instructions. The memory unit409 may also be configured to store the timing compatibility hierarchyand/or control timing configuration candidate or ordered sets. Thememory unit 409 may be any suitable type of computer readable memory andmay be of volatile and/or non-volatile type.

The node 400 may further comprise an analyzing unit 413 which isconfigured to analyze and determine a control timing configurationnumber or setting for UL and DL communications. The node furthercomprises an establishment unit 415 which is configured to assign thecontrol timing configuration number or setting for UL and DLcommunications to a user equipment. The node 400 may further comprise anarrangement unit 411 that may be configured to arrange the timingconfigurations in a hierarchical structure or provide and/or order thecandidate or ordered sets.

The determining unit, assigning unit, and/or the arrangement unit may beany suitable type of computation unit, e.g. a microprocessor, digitalsignal processor (DSP), field programmable gate array (FPGA), orapplication specific integrated circuit (ASIC). It should be appreciatedthat the determining unit, assigning unit, and/or the arrangement unitmay be comprised as a single unit or any number of units.

FIG. 27 is a flow diagram depicting example operations which may betaken by the network node 400 for determining at least one timingconfiguration number for a plurality of aggregated cells of a multiplecell communications network. Each aggregated cell is associated with anuplink-downlink configuration number, where at least two uplink-downlinkconfiguration numbers of the plurality of aggregated cells are notequal. The aggregated cells are associated with a user equipment in themultiple cell communications network.

Example Operation 10:

The network node 400 is configured to analyze 10 at least two orderedsets of timing configuration numbers. Each of the ordered setcorresponds to a respective cell associated with the user equipment inthe multiple cell communications network. The analyzing unit 413 isconfigured to perform the analyzing 10.

Example Operation 11:

According to some of the example embodiments, the analyzing 10 mayfurther comprise reading 11 each ordered set of timing configurationnumbers from memory 409. The analyzing unit 413 may be configured toperform the reading 11.

Example Operation 12:

According to some of the example embodiments, the reading 11 may furthercomprise using 12 each of the uplink-downlink configuration numbers ofthe corresponding cells associated with the user equipment as an indexto access the memory 409. The analyzing unit 413 may be configured toperform the using 12.

Example Operation 13:

According to some of the example embodiments, the analyzing 10 mayfurther comprise arranging 13 the timing configuration numbers in eachrespective ordered set based on a subframe timing compatibility, forexample, as described in relation to FIG. 15. The arrangement unit 411may be configured to perform the arranging 13.

Example Operation 14:

According to some of the example embodiments, the arranging 13 may alsocomprise arranging 14 respective timing configuration numbers for uplinkcontrol timing such that timing configuration numbers which appear lateror earlier in the ordered set correspond to uplink-downlinkconfigurations which comprise uplink subframes that form a superset ofall uplink subframes from uplink-downlink configurations associated withtiming configuration numbers which appear earlier or later,respectively, in the ordered set. The arrangement unit 411 may beconfigured to perform of arranging 14. It should also be appreciatedthat the subframe timing compatibility may be prearranged by anothermeans.

It should be appreciated that each ordered set may comprise one timingconfiguration number that is equal to the uplink-downlink configurationnumber of the corresponding cell. It should also be appreciated thateach ordered set may further comprise one timing configuration numberthat is equal to the uplink-downlink configuration number of thecorresponding cell as a first or last timing configuration number.

Example Operation 16:

According to some of the example embodiments, the arranging 13 may alsocomprise arranging 16 respective timing configuration numbers fordownlink HARQ control timing such that timing configuration numberswhich appear later or earlier in the ordered set correspond touplink-downlink configurations which comprise downlink subframes thatform a superset of all downlink subframes from uplink-downlinkconfigurations associated with timing configurations numbers whichappear earlier or later, respectively, in the ordered set. Thearrangement unit 411 may be configured to perform of arranging 16. Itshould also be appreciated that the subframe timing compatibility may beprearranged by another means.

It should be appreciated that each ordered set may comprise one timingconfiguration number that is equal to the uplink-downlink configurationnumber of the corresponding cell. It should also be appreciated thateach ordered set may further comprise one timing configuration numberthat is equal to the uplink-downlink configuration number of thecorresponding cell as a first or last timing configuration number.

Example Operation 18:

The node 400 is configured to assign 18 at least one timingconfiguration number from the at least two ordered sets of timingconfiguration numbers. According to an example of embodiments, theassigning 18 is based on a result from the analyzing 10, e.g. asdisclosed earlier in relation to Table 4 and the examples referring toTable 4. The establishment unit 415 is configured to perform theassigning 18. The assigning may also further be based on results fromany of the preceding operations 11, 12, 13, 14, and 16.

It should be appreciated that the at least one timing configurationnumber may be indicative of an uplink control timing configurationnumber for establishing uplink scheduling grant and/oracknowledgement/negative-acknowledgement, A/N, timings across allaggregated cells associated with the user equipment. It should also beappreciated that the at least one timing configuration number may beindicative of a downlink Hybrid-Automatic Repeat Request, HARQ, controltiming for establishing downlink HARQ A/N timings across all aggregatedcells associated with the use equipment.

According to embodiments the timing configuration numbers may be seen ascontrol timing configuration number used to set subframe timing. Theassigning 18 may further be seen as assigning 18 at least one controltiming configuration number from said at least two ordered sets ofcontrol timing configuration numbers as a common control timingconfiguration number for each of the plurality of aggregated cells ofthe multiple cells communications network. Basically, assigning is donefor a common control timing configuration number which will be suitablefor all of the cells.

Example Operation 20:

According to some of the example embodiments, the assigning 18 furthercomprise assigning 20 the timing configuration number based on anintersection of the at least two ordered sets of timing configurationnumbers. The establishment unit 415 may be configured to perform theassigning 20.

Example Operation 22:

According to some of the example embodiments, the assigning 20 furthercomprise assigning 22 a first or last timing configuration number in theintersection. For example, the intersection may also be ordered, thusthe assignment may be made with respect to the first or last timingconfiguration number, as explained, e.g., in relation to table 4 and theexample provided thereafter. The establishment unit 415 may beconfigured to perform the assigning 22.

CONCLUSION

The description of the example embodiments provided herein have beenpresented for purposes of illustration. The description is not intendedto be exhaustive or to limit example embodiments to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of various alternativesto the provided embodiments. The examples discussed herein were chosenand described in order to explain the principles and the nature ofvarious example embodiments and its practical application to enable oneskilled in the art to utilize the example embodiments in various mannersand with various modifications as are suited to the particular usecontemplated. The features of the embodiments described herein may becombined in all possible combinations of methods, apparatus, modules,systems, and computer program products. It should be appreciated thatthe example embodiments presented herein may be practiced in anycombination with each other.

It should be noted that the word “comprising” does not necessarilyexclude the presence of other elements or steps than those listed andthe words “a” or “an” preceding an element do not exclude the presenceof a plurality of such elements. It should further be noted that anyreference signs do not limit the scope of the claims, that the exampleembodiments may be implemented at least in part by means of bothhardware and software, and that several “means”, “units” or “devices”may be represented by the same item of hardware and/orcircuits/circuitries.

A “device” as the term is used herein, is to be broadly interpreted toinclude a radiotelephone having ability for Internet/intranet access,web browser, organizer, calendar, a camera (e.g., video and/or stillimage camera), a sound recorder (e.g., a microphone), and/or globalpositioning system (GPS) receiver; a personal communications system(PCS) user equipment that may combine a cellular radiotelephone withdata processing; a personal digital assistant (PDA) that may include aradiotelephone or wireless communication system; a laptop; a camera(e.g., video and/or still image camera) having communication ability;and any other computation or communication device capable oftransceiving, such as a personal computer, a home entertainment system,a television, etc.

Although the description is mainly given for a user equipment, asmeasuring or recording unit, it should be understood by the skilled inthe art that “user equipment” is a non-limiting term which means anywireless device, terminal, or node capable of receiving in DL andtransmitting in UL (e.g. PDA, laptop, mobile, sensor, fixed relay,mobile relay or even a radio base station, e.g. femto base station).

A cell is associated with a radio node, where a radio node or radionetwork node or eNodeB used interchangeably in the example embodimentdescription, comprises in a general sense any node transmitting radiosignals used for measurements, e.g., eNodeB, macro/micro/pico basestation, home eNodeB, relay, beacon device, or repeater. A radio nodeherein may comprise a radio node operating in one or more frequencies orfrequency bands. It may be a radio node capable of CA. It may also be asingle- or multi-RAT node. A multi-RAT node may comprise a node withco-located RATs or supporting multi-standard radio (MSR) or a mixedradio node.

The various example embodiments described herein are described in thegeneral context of method steps or processes, which may be implementedin one aspect by a computer program product, embodied in acomputer-readable medium, including computer-executable instructions,such as program code, executed by computers in networked environments. Acomputer-readable medium may include removable and non-removable storagedevices including, but not limited to, Read Only Memory (ROM), RandomAccess Memory (RAM), compact discs (CDs), digital versatile discs (DVD),etc. Generally, program modules may include routines, programs, objects,components, data structures, etc. that perform particular tasks orimplement particular abstract data types. Computer-executableinstructions, associated data structures, and program modules representexamples of program code for executing steps of the methods disclosedherein. The particular sequence of such executable instructions orassociated data structures represents examples of corresponding acts forimplementing the functions described in such steps or processes.

In the drawings and specification, there have been disclosed exemplaryembodiments. However, many variations and modifications may be made tothese embodiments. Accordingly, although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation, the scope of the embodiments being defined bythe following claims.

The invention claimed is:
 1. A method, in a network node, fordetermining at least one timing configuration number to use forconfiguring the timing of control signalling across a plurality ofaggregated cells of a multiple cell communications network, eachaggregated cell being associated with an uplink-downlink configurationnumber that indexes an uplink-downlink configuration defining uplink anddownlink resources for that cell, wherein at least two uplink-downlinkconfiguration numbers of the plurality of aggregated cells are notequal, and said plurality of aggregated cells being associated with auser equipment, the method comprising: analysing at least two orderedsets of timing configuration numbers, wherein different timingconfiguration numbers index different control timing configurations thatconfigure the timing of control signalling differently for differentuplink-downlink configurations, wherein each ordered set corresponds toa respective cell associated with the user equipment in the multiplecell communications network and includes timing configuration numbersordered based on how compatible the corresponding control timingconfigurations are with the uplink-downlink configuration of thatrespective cell; and assigning, for configuring the timing of controlsignalling across the plurality of aggregated cells, at least one timingconfiguration number from said at least two ordered sets of timingconfiguration numbers.
 2. The method of claim 1, wherein the at leastone timing configuration number is indicative of a downlinkHybrid-Automatic Repeat Request, HARQ, control timing configuration forestablishing downlink HARQ A/N timings across the plurality ofaggregated cells.
 3. The method of claim 1, wherein the at least onetiming configuration number is indicative of an uplink control timingconfiguration number for establishing at least one of uplink schedulinggrant and acknowledgement/negative-acknowledgement, A/N, timings acrossthe plurality of aggregated cells.
 4. The method of claim 1, wherein theanalysing further comprises reading each ordered set of timingconfiguration numbers from memory.
 5. The method of claim 4, wherein thereading further comprises using each of the uplink-downlinkconfiguration numbers of the corresponding cells associated with theuser equipment as an index to access the memory.
 6. The method of claim1, wherein the timing configuration numbers in each respective orderedset are ordered based on a subframe timing compatibility.
 7. The methodof claim 6, wherein each ordered set comprises timing configurationnumbers for uplink control timing such that timing configuration numberswhich appear later or earlier in the ordered set correspond touplink-downlink configurations which comprise uplink subframes that forma superset of all uplink subframes of uplink-downlink configurationsassociated with timing configuration numbers which appear earlier orlater, respectively, in the ordered set.
 8. The method of claim 6,wherein each ordered set comprises timing configuration numbers fordownlink HARQ control timing such that timing configuration numberswhich appear later or earlier in the ordered set correspond touplink-downlink configurations which comprise downlink subframes thatform a superset of all downlink subframes of uplink-downlinkconfigurations associated with timing configuration numbers which appearearlier or later, respectively, in the ordered set.
 9. The method ofclaim 1, wherein each ordered set comprises one timing configurationnumber that is equal to the uplink-downlink configuration number of saidcorresponding cell.
 10. The method of claim 9, wherein each ordered setfurther comprises one timing configuration number that is equal to theuplink-downlink configuration number of said corresponding cell as thefirst or last, respectively, timing configuration number in the orderedset.
 11. The method of claim 1, wherein the assigning further comprisesassigning the at least one timing configuration number based on anintersection of said at least two ordered sets of timing configurationnumbers.
 12. The method of claim 11, wherein the assigning furthercomprises assigning a first or a last timing configuration number in theintersection.
 13. The method of claim 1, wherein the assigning furthercomprises assigning one timing configuration number for uplink controltiming and one timing configuration number for downlink control timing.14. The method of claim 1, wherein the uplink-downlink configurationsare time division duplex (TDD) configurations.
 15. A network node fordetermining at least one timing configuration number to use forconfiguring the timing of control signalling across a plurality ofaggregated cells of a multiple cell communications network, eachaggregated cell being associated with an uplink-downlink configurationnumber that indexes an uplink-downlink configuration defining uplink anddownlink resources for that cell, wherein at least two uplink-downlinkconfiguration numbers of the plurality of aggregated cells are notequal, and said plurality of aggregated cells being associated with auser equipment, the network node comprising: an analysing circuitconfigured to analyse at least two ordered sets of timing configurationnumbers, wherein different timing configuration numbers index differentcontrol timing configurations that configure the timing of controlsignalling differently for different uplink-downlink configurations,wherein each ordered set corresponds to a cell associated with the userequipment in the multiple cell communications network and includestiming configuration numbers ordered based on how compatible thecorresponding control timing configurations are with the uplink-downlinkconfiguration of that respective cell; and an establishment circuitconfigured to assign, for configuring the timing of control signallingacross the plurality of aggregated cells, at least one timingconfiguration number from said at least two ordered sets of timingconfiguration numbers.
 16. The network node of claim 15, wherein thenetwork node is one of the user equipment, a base station, and a relaynode.
 17. The network node of claim 15, wherein the at least one timingconfiguration number is indicative of a downlink Hybrid-Automatic RepeatRequest, HARQ, control timing configuration for establishing downlinkHARQ A/N timings across the plurality of aggregated cells.
 18. Thenetwork node of claim 15, wherein the at least one timing configurationnumber is indicative of at least one of an uplink control timingconfiguration number for establishing uplink scheduling grant andacknowledgement/negative-acknowledgement, A/N, timings across theplurality of aggregated cells.
 19. The network node of claim 15, whereinthe analysing circuit is further configured to read each ordered set oftiming configuration numbers from memory.
 20. The network node of claim19, wherein the analysing circuit is further configured to utilize eachof the uplink-downlink configuration numbers of the corresponding cellsassociated with the user equipment as an index to access the memory. 21.The network node of claim 15, wherein the timing configuration numbersin each respective ordered set are ordered based on a subframe timingcompatibility.
 22. The network node of claim 21, wherein each orderedset comprises respective timing configuration numbers for uplink controltiming such that timing configuration numbers which appear later orearlier in the ordered set correspond to uplink-downlink configurationswhich comprise uplink subframes that form a superset of all uplinksubframes of uplink-downlink configurations associated with timingconfiguration numbers which appear earlier or later, respectively, inthe ordered set.
 23. The network node of claim 21, wherein each orderedset comprises respective timing configuration numbers for downlink HARQcontrol timing such that timing configuration numbers which appear lateror earlier in the ordered set correspond to uplink-downlinkconfigurations which comprise downlink subframes that form a superset ofall downlink subframes of uplink-downlink configurations associated withtiming configuration numbers which appear earlier or later,respectively, in the ordered set.
 24. The network node of claim 15,wherein each ordered set comprises one timing configuration number thatis equal to the uplink-downlink configuration number of saidcorresponding cell.
 25. The network node of claim 24, wherein eachordered set further comprises one timing configuration number that isequal to the uplink-downlink configuration number of said correspondingcell as the first or last, respectively, timing configuration number inthe ordered set.
 26. The network node of claim 15, wherein theestablishment circuit is further configured to assign the at least onetiming configuration number based on an intersection of said at leasttwo ordered sets of timing configuration numbers.
 27. The network nodeof claim 26, wherein the establishment circuit is further configured toassign a first or a last timing configuration number in theintersection.
 28. A computer program product stored in a non-transitorycomputer readable medium for controlling a network node that determinesat least one timing configuration number to use for configuring thetiming of control signalling across a plurality of aggregated cells of amultiple cell communications network, each aggregated cell beingassociated with an uplink-downlink configuration number that indexes anuplink-downlink configuration defining uplink and downlink resources forthat cell, wherein at least two uplink-downlink configuration numbers ofthe plurality of aggregated cells are not equal, and said plurality ofaggregated cells being associated with a user equipment, the computerprogram product comprising software instructions which, when run on thenetwork node, causes the network node to: analyze at least two orderedsets of timing configuration numbers, wherein different timingconfiguration numbers index different control timing configurations thatconfigure the timing of control signalling differently for differentuplink-downlink configurations, wherein each ordered set corresponds toa respective cell associated with the user equipment in the multiplecell communications network and includes timing configuration numbersordered based on how compatible the corresponding control timingconfigurations are with the uplink-downlink configuration of thatrespective cell; and assign, for configuring the timing of controlsignalling across the plurality of aggregated cells, at least one timingconfiguration number from said at least two ordered sets of timingconfiguration numbers.